JPS5930236Y2 - Control device for variable displacement hydraulic pump - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a device for controlling the discharge amount of a variable displacement hydraulic pump.

2. Description of the Related Art In variable displacement hydraulic pumps, there have been conventional devices that control the flow rate by changing the pump angle based on the discharge pressure.

This conventional device balances the discharge pressure of the pump with a receiving piston and a spring, and as the pressure increases, the angle of the pump decreases.Due to the characteristics of the spring, it forms a curve as shown in Figure 1. ,
When the flow rate increases beyond a certain level, the pressure decreases, and there is a problem in that the pressure cannot be maintained constant.

For example, the actuator A1, such as a large number of hydraulic motors, is installed in the hydraulic pump discharge piping. A2...An is connected,
It is assumed that a flow control valve or the like is installed at each inlet to control the amount of flow into the actuator.

If the actuator A1 requests a flow rate of Ql, and the actuator A2 requests a flow rate of Q2, the minimum required discharge amount of the hydraulic pump is Ql+Q2+α (where α is the amount of leakage of pulp, etc.).

In this way, the hydraulic pump is connected to the actuator A1. A2...
・・・・The total needle of the required amount of simultaneous operation in An is kept at a constant pressure P.
If it is possible to discharge water while maintaining the same, a variable displacement hydraulic pump having this control device can be said to be an energy-saving hydraulic pump unit.

Energy-saving hydraulic pumps that meet these demands include a method in which a four-way guide valve or a nozzle flapper type valve is directly connected to a servo motor of a variable displacement hydraulic pump, but it is also possible to control it by directly connecting a servo motor of a variable displacement hydraulic pump. In large devices, the combination of a non-positioning four-way guide valve and a non-positioning servo motor poses a problem in the stability of the entire device, and circuit design is often difficult.

The present invention was developed to solve the above problems, and uses a positional controller to change the secondary pressure of the pressure reducing valve, thereby changing the control pressure to the pressure receiving piston and determining the pump angle. The present invention provides a control device for a variable displacement hydraulic pump.

Next, one embodiment of the present invention will be explained with reference to FIG.
is a variable displacement hydraulic pump, and the discharge side of this pump 1 is connected to pipelines L1, L2 and a predetermined number of switching valves 20.
Through the actuator A□, such as a plurality of hydraulic motors,
A2...Connected to An.

Actuator A1. The discharge side of A2...An is connected to the tank T via a line L3.

A lie L4 branched from the line L1 is connected to a pressure reducing valve 2, and the pressure reducing valve 2 is connected to a spring balance type controller 3 that controls the pump angle by a line L5.
The next pressure is now acting on the pump controller.

The adjusting spring 4 of the pressure reducing valve 2 is supported on a seat 5 provided on a pressure responsive piston 6.

Pressure-responsive valve 7 such as a four-way guide valve or a nozzle flapper type valve
The ports 8 and 9 are respectively connected to the line L4 via lines L6yL7, and a pressure receiving portion 11 of a spool 10 is pressed onto the boat 8 by a spring 12.

Ports N3 and 14 of the valve 7 are connected to ports N6 and 17 of the cylinder 15 housing the piston, respectively, by lines L8jL9.

Note that ACC is an accumulator appropriately provided on line L2.

Next, to explain the operation of the present invention, the oil discharged from the hydraulic pump 1 is supplied to the line L1. suitable actuator A1 via L2
, A2... is sent to An.

Therefore, when one of the actuators becomes unused and a predetermined switching valve 20 is closed, the discharge pressure P of the pump 1 increases.

Then, the pressure P is line L□. L4. The pressure oil of line L7 is transmitted to the pressure receiving part 11 via L6, and the spool 10 moves to the right.
9 and acts on the right side of the piston 6.

Therefore, the piston 6 moves to the left, and the set pressure of the spring 4 of the pressure reducing valve 2 increases.

That is, the pressure on the controller 3 of the pump 1 increases, the pump angle decreases, and the discharge amount decreases.

Conversely, when the pump discharge pressure P decreases, the spoo/l'IO
moves to the left, pressure oil in line L7 flows to line L8 and acts on the left side of piston 6, piston 6 moves to the right, the set pressure of spring 4 decreases, the pump angle increases and discharge The amount increases.

In this way, the pump angle is adjusted to a flow rate that meets the load requirement while keeping the discharge pressure P constant, and the characteristics shown in FIG. 3 can be obtained.

As explained above, in this invention, a spring balance type controller is controlled by a pressure reducing valve, so the pump itself can be controlled with a stable curve according to the spring constant, and stable characteristics can be obtained simply by the servo valve cylinder. .

Further, by using a spring balance type controller and adding a four-way guide valve, etc., it is possible to easily obtain a characteristic of constant pressure, so that the overall cost can be reduced.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of discharge pressure and flow rate of a conventional variable displacement hydraulic pump, Fig. 2 is a diagram showing an embodiment of a control device for a variable displacement hydraulic pump according to the present invention, and Fig. 3 is a diagram showing the characteristic curve of the discharge pressure and flow rate of a conventional variable displacement hydraulic pump. FIG. 2 is a characteristic diagram of discharge pressure and flow rate of a hydraulic pump controlled by the hydraulic pump. 1... Variable displacement hydraulic pump, 2...
Pressure reducing valve, 3...Controller, 4...Spring', 7...Four-way guide valve, A1. A2...
...An...actuator.

Claims (1)

[Scope of utility model registration request] In a device in which the angle of a variable displacement hydraulic pump that sends oil to a plurality of actuators is controlled by a controller 3, the discharge pressure of the pump is guided to the controller via a pressure reducing valve 2, and the pressure regulating spring 4 of the pressure reducing valve is A control device for a variable displacement hydraulic pump, characterized in that a set pressure is controlled by a piston 6 that receives pump discharge pressure via a pressure-responsive switching device 7 of a four-way guide valve or the like.